Method and apparatus for producing mobile radio signals

ABSTRACT

A method and device are provided for producing mobile radio signals, which utilize a direct conversion receiver, at least one first and one second local oscillator and one regenerative divider for processing signals according to different mobile radio standards. For generating the intermediate frequency for transmission according to at least one of the mobile radio standards, a division by four in addition to a division by three of the oscillator frequency is also possible.

[0001] The present invention relates to a method and a device for producing mobile radio signals as described in the precharacterizing clause of the independent claims.

[0002] Over the course of recent years, wireless communication networks and mobile radio networks have developed to become an important component in the communications infrastructure on a worldwide scale. As a result of the enormous demand for mobile radio capacity, various industry-standard communication technologies have been developed based on digital modulation techniques. Thus, for example, Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA) and also frequency hopping techniques have been used in order to develop modern communication systems. Following parallel implementation of systems of these types, it has proved to be advantageous to provide receivers which are capable of operating with one or more of these standard techniques. In order to make this possible, it is necessary to provide a receiver which is capable of receiving signals that have been modulated using different modulation techniques.

[0003] In Central Europe in particular, but also in other regions of the world, the GSM mobile radio system has been developed in this context, whereby different frequency ranges are made available within this system. The next few years will see the advent of the next generation of mobile radio standard (UMTS, 3G) which will encompass additional frequency ranges.

[0004] From the standpoint of the manufacturer of terminal equipment, it is therefore becoming increasingly more difficult to guarantee signal generation for the different bands and standards at an acceptable level of resource deployment and conversely to provide the corresponding receive facilities, in particular on condition that the number of oscillators used and their required tuning range should be kept as small as possible.

[0005] Known receivers for processing signals employing different modulation standards implement the double conversion receiver architecture, for example. The double conversion receiver architecture is distinguished by the fact that the received radio signal is converted to an intermediate frequency signal and the intermediate frequency signal is then converted downward into the base band. In addition, the intermediate frequency is also delivered to a gain check. However, double conversion receivers have the disadvantage that they require a large number of circuitry components, which increases the costs, the size and also the power draw of the receiver.

[0006] An alternative to these double conversion receivers is offered by direct conversion receivers which have no intermediate frequency and therefore have no resource requirement in respect of filtering for the intermediate frequency. For receiving, two thirds or four thirds of the oscillator frequency, which is used for downconversion of the receive signal into the base band, is generated optionally from a first local oscillator or from a second local oscillator by means of a regenerative divider.

[0007] In this situation, for transmission, use is made of the fact that the regenerative divider also generates one third of the oscillator frequency as a “waste product”. This is subsequently IQ-modulated and delivered to an offset PLL (phase-locked-loop) which steps it up to the actual transmit frequency. For the special UTMS application situation, the output signal is generated by mixing with the first local oscillator since in this case an amplitude-modulated signal must be present, which cannot be achieved with an offset PLL.

[0008] The disadvantage of this solution is the fact that the first local oscillator must have a broad tuning range from 1282.5 to 1452.5 MHz. This is not only difficult to implement but under certain circumstances even necessitates the use of two separate oscillators for the respective sub-ranges. Furthermore, the offset PLL likewise contains two oscillators internally which make significant demands in terms of their space requirement.

[0009] The object of the present invention is therefore to provide a method and a device of the generic type in which as small a number of oscillators as possible is used and the requisite tuning range is as small as possible, whereby the solution should be capable of being implemented as cost-effectively and simply as possible.

[0010] This object is achieved by the features of the independent claims, whereby useful embodiments are described by the features of the respective subclaims.

[0011] Firstly, a method is provided for generating mobile radio signals by means of a direct conversion receiver, using at least one first and one second local oscillator and also a regenerative divider for dividing the respective oscillator frequency by three, for processing signals which conform to different mobile radio standards, characterized in that an intermediate frequency is produced during transmission for at least one of the mobile radio standards to be processed as a result of dividing one of the local oscillators by four.

[0012] A divider of this type having the factor 4 or a multiple thereof can be easily integrated in silicon without a major resource requirement.

[0013] By preference, the method is designed in such a manner in accordance with the present invention that optionally a frequency division by three or a frequency division by four can take place.

[0014] Apart from the two local oscillators described, it is also possible to use a larger number of local oscillators. In addition, by preference, the local oscillator frequency IQ divided by three or by four is modulated, whereby the modulated signal can be delivered jointly with one of the unmodulated local oscillator signals to an offset PLL or alternatively, instead of to an offset PLL, it can also be delivered to a mixer.

[0015] The oscillator frequencies can moreover also be higher than described above by an integer factor, for example by a factor of 2, whereby a division of the frequency by six or by eight would be required.

[0016] In addition, the invention relates to an arrangement for generating mobile radio signals, for executing the method as described above.

[0017] Further features and advantages of the present invention will emerge from the description which follows of a preferred embodiment in conjunction with the accompanying drawings. In the drawings:

[0018]FIG. 1 shows an embodiment of an arrangement according to the present invention; and

[0019]FIG. 2 shows a variant of the embodiment according to FIG. 1.

[0020]FIG. 1 shows an embodiment of an arrangement for generating mobile radio signals. In this situation, the embodiment in this illustration includes a direct conversion receiver 2 which has no intermediate frequency and therefore has no resource requirement in respect of filtering for the intermediate frequency. With regard to the receive signal 4, in the embodiment illustrated these are GSM signals in the range 925 to 960 MHz, DCS signals in the range 1805 to 1880 MHz and also UMTS signals in the range 2110 to 2170 MHz. In addition, the direct conversion receiver 2 has an IQ output 6. For receiving, two thirds or four thirds of the oscillator frequency, which is used for downconversion of the receive signal into the base band, is generated optionally from a first local oscillator 8 or from a second local oscillator 10 by means of a regenerative divider 12. For transmission, use is also made of the fact that the regenerative divider 12 also generates one third of the oscillator frequency as a “waste product”. It is IQ-modulated in an IQ modulator 14 and subsequently delivered to an offset PLL 16 which steps it up to the actual transmit frequency. For UMTS, the output signal is generated by mixing 20 with the first local oscillator 8 since in this case an amplitude-modulated signal must be generated, which can not be achieved with an offset PLL.

[0021] For transmission, the intermediate frequency for GSM and UMTS is produced by the regenerative divider 12 by dividing the second local oscillator 10 by three, for DCS however the intermediate frequency is produced by dividing the second local oscillator 10 by four. In this manner, the first local oscillator 8 needs to provide coverage in only a single range from 1330 to 1452.5 MHz and the second local oscillator 10 a range from 1520 to 1627.5 MHz. The number of oscillators used in this situation remains unchanged.

[0022]FIG. 2 shows a variant of the embodiment according to FIG. 1, whereby the same reference characters are used for the corresponding elements. In this case, the modulated intermediate frequency is filtered in a corresponding low-pass filter 22 and subsequently converted into the transmit band not by means of an offset PLL as shown in FIG. 1 but by mixing 24 with the first local oscillator 8. This also makes it possible to transmit amplitude-modulated signals in the case of GSM and DCS, with the result that extensions of the standard, such as Edge for example, can also be taken into consideration. It is advantageous here that with the offset PLL the latter's oscillators are also dispensed with, whereby filtering measures such as a diplexer 24 and an LO lock are provided in contrast to the variant according to FIG. 1.

[0023] Signal generation for the different bands and standards is guaranteed at an acceptable level of resource deployment, and conversely the corresponding receive facilities are provided, by means of the method presented and the corresponding arrangement, whereby the number of oscillators used and their required tuning range is kept as small as possible. 

1. Method for producing mobile radio signals by means of a direct conversion receiver, using at least one first and one second local oscillator and also a regenerative divider for dividing the respective oscillator frequency by three, for processing signals which conform to different mobile radio standards, characterized in that during transmission, an intermediate frequency is produced for at least one of the mobile radio standards to be processed by dividing one of the local oscillators by four.
 2. Method according to claim 1, characterized in that the respective oscillator frequency is IQ-modulated.
 3. Method according to claim 2, characterized in that the modulated signal is delivered jointly with one of the unmodulated local oscillator signals to an offset PLL.
 4. Method according to claim 2, characterized in that the modulated signal is delivered jointly with one of the unmodulated local oscillator signals to a mixer.
 5. Device for producing mobile radio signals, comprising a direct conversion receiver, at least one first and one second local oscillator and a regenerative divider for dividing the respective oscillator frequency by three, characterized in that in addition a divider (18) having the factor 4 is provided.
 6. Device according to claim 5, characterized in that an IQ modulator (14) is provided which is used to modulate the oscillator frequency that has been divided by three or four.
 7. Device according to claim 6, characterized in that an offset PLL (16) is provided for processing the modulated signal jointly with one of the unmodulated oscillator signals.
 8. Device according to claim 7, characterized in that a mixer (20) is provided for mixing the modulated signal jointly with one of the unmodulated oscillator signals. 